Tuesday, October 17, 2017, 15:45 - Over the years, there's been some debate about whether or not ride-hailing apps like Uber and Lyft help or hinder public transportation and road congestion.

A 2016 study by the University of Arizona, for example, concludes the apps have a positive effect on Seattle's congestion while a 2017 study by traffic analyst Bruce Schaller contributes to a 3% to 4% jump in NYC gridlock.

A new study, published earlier this month and the largest of its kind to date, aims to set the record straight.

The paper, authored by transportation researchers at U.C. Davis, looks at the behaviour of 4,000 app users in major U.S. cities (including Seattle and NYC) between 2014 and 2016. It operates under a simple premise, best surmised up by Amanda Eaken, deputy director of urban solutions and sustainable communities at the Natural Resources Defense Council, who partnered with U.C. Davis for the research:

“If you hadn’t just taken a trip using Uber or Lyft, what would you have done instead?”

It turns out a significant number of people would have simply stayed home or opted for a more environmentally-friendly means of transportation: According to the paper, between 49% and 61% of trips taken would not have been made at all, or would have been made by walking, biking or with public transit.

In addition to adding more cars on the road, the apps don't seem to be inspiring people to ditch their cars, either. The paper instead notes an uptick in users cancelling their memberships to car-sharing services like Zipcar, where cars can be picked up and dropped off in different locations.

For users who don't use transit, it's found “the majority of ride-hailing users (91%) have not made any changes with regards to whether or not they own a vehicle,” and "those who have reduced the number of cars they own and the average number of miles they drive personally have substituted those trips with increased ride-hailing use."

Ride-hailing seems to be attracting people away from bus services with about a 6% reduction and light rain services by 3 percent. The top two reasons users are opting for ride-hailing apps is to avoid parking headaches, followed by drinking. People aged 18 to 29 are the most frequent users.

"Ride-hailing services have exploded in popularity around the world in a relatively short period of time, and initial evidence suggests that they capture a relatively significant share of how people travel in major cities," the study reads.

"Without a clear understanding of how these services influence transportation decisions, cities will be limited in their ability to make effective mid- to long-range infrastructure and policy choices aimed at ensuring that transportation services are equitable, sustainable, and safe."

The authors say more research is needed to understand how ride-hailing apps contribute to traffic congestion and, by extension, pollution.

In the meantime, the paper is calling on city planners to give priority to high-occupancy vehicles on roadways and improve data access to transportation planners.